1. Field of the Invention
This invention relates to a mid-mount mower having a mower unit vertically movably suspended from a body frame between front wheels and rear wheels. This mower unit has rotary blades rotatable about three vertical axes arranged sideways inside a mower deck, and a mower input shaft disposed on the mower deck to transfer power to the rotary blades. The mower input shaft extends longitudinally of the body frame, and a rear connecting end. The mower input shaft is connected through a universal joint by a relay transmission shaft to a PTO shaft provided in a rear transmission mechanism for driving the rear wheels.
2. Description of the Related Art
In a mower unit attachable to a lawn mower having the above construction, as disclosed in Japanese Patent Publication (Unexamined) No. 2002-67721, for example, the top board of the mower deck has a front portion arched to define a tunnel therein. Grass clippings flying from the front half of the rotating track of each rotary blade are transported along the tunnel to a grass discharge opening formed at one end of the mower deck. Such a mower unit is in wide use.
The mower deck with the grass-transmitting tunnel formed in the front portion thereof has a low rear portion. A blade-driving input shaft disposed on the mower deck is also low. Thus, even if the PTO shaft is disposed in a low rearward position of the vehicle body, the mower deck raised to a large extent never interferes with the universal joint.
The mower unit having the mower deck with the tunnel is suited for an operating mode for transporting grass clippings along the tunnel and discharging the clippings from one end of the deck (side discharge). However, the deck except the tunnel portion is insufficient in depth for a mulching operation for cutting the grass clippings into still smaller pieces and depositing them on the ground. It is difficult to cut the grass clippings into small pieces efficiently by retaining the grass clippings as entrained by rotation of the rotary blades for a sufficiently long time in mulching chambers (enclosures) formed in the mower deck. Thus, it has been proposed to enable a selection of a grass cutting operation in the side discharge mode or a mulching operation by using a flat mower deck having an increased and uniform overall depth.
However, with a flat deck structure in which the entire upper surface of the mower deck has a uniform height over the ground to increase the depth of its internal space, the blade-driving mower input shaft disposed on the mower deck has an increased height. Where this mower input shaft and the PTO shaft in the rearward position of the body frame are operatively interconnected through a universal joint and a transmission shaft as in the prior art, the rear end of the mower deck tends to interfere with the shaft transmission portion when the mower unit is raised. It is difficult to secure a sufficient height for raising the mower unit. Naturally, where the PTO shaft is installed in a high location, the mower unit may be raised high without the above interference. To install the PTO shaft in a high location, the rear transmission mechanism must also be disposed in a high location. This results in a different inconvenience that the center of gravity of the vehicle body is raised.